Habitat and Ecology

Habitat and Ecology

Significant differences have been recorded among encounter rates of dolphins in the Mahakam for eight 40-km long segments of the river mainstem and tributaries (χ² = 35.91, df = 7, P et al. 2007).

The average daily home ranges of 27 groups, which were followed for more than six hours, was 10 km of river length (SD = 8.6, range = 1-45 km). River length ranges were also calculated for 53 photo-identified dolphins during 3.5 consecutive years. Individuals were identified on average 12.5 times (SD = 9.5, range = 2-39) and during 6.2 different survey days (SD = 3.7, range = 2-20). These dolphins moved within the river an average of 61 linear km (SD = 44, range = 4-181) (Kreb et al. 2007).